changed documentation to create custom Assets
Added carriage returns (\r) to lines written to DDL file.

DDL generated by Ebean uses \r\n. This patch makes Play also use \r\n so the file will have consistent line endings.
More details at https://groups.google.com/forum/#!topic/play-framework/-H0MgRPFd60

Review by @jroper
Backport to 2.0.x
Fixing status in test case (should be 303 not 302)
Added 'an' to wording when database is in an inconsistent state